"According to L2 information, Test stand A-1 modifications were completed June 30, with engine E0525 mounted on the stand July 1. E0525 testing is still scheduled to start NET (No Earlier Than) August 20"

"Unfortunately there is a lot of oversimplification going on in this thread which could lead to an inaccurate understanding of several complex subjects regarding the SSME and its upgrade. The block upgrade (from Phase II+ to Block I to Block II) took almost a decade and cost over $2B. The intention was to provide a more robust engine, not just because of some pad abort that occurred. The newer block engine had lower ISP (by about 1.5 sec) which required an increase in thrust from 104% RPL to 104.5%RPL to make up for the performance loss. Neither engine was certified for 109% operation but that was certainly the intent for the Block II engine. Both nominal flight and all intact aborts used the 104.5% RPL thrust level. During testing to certify the 109% for aborts, it was found that there were components in the main propulsion piping in the orbiter which likely could not withstand the higher vibration environment associated with that flow rate. Cracking of the metallic components could have lead to liberation of metal pieces into the engine inlet which would not have been good at the pumps. So efforts to certify 109% or 111% were terminated. 109% throttles were authorized only in 'do or die' contingency abort scenarious which were multiple failures deep."

In light of the issues which were proven at the 109% RPL using the existing Shuttle MPS piping. 1)Does this mean that the MPS piping/valves/hardware removed from the OV's would not be used on the test stand?2) Was the Shuttle MPS piping/valves etc. removed from the Orbiters just in case the SLS core stage used 3 RS25 engine, and now that 4 engines will be used, that MPS hardware is not able to be used on thetest stand or as flight hardware?

3) Will any 111%RPL be tested, or do abort modes such as an ATO(Abort to Orbit), such as an engine out later in the 2nd stage after the solid boosters have jettisoned, increase the remaining 3 RS25's to 111%RPL to help reach a more desireable velocity, or do these Shuttle'esque off-nominal engine thrust settings/ATO scenarios not apply to SLS?

My understanding is that the existing RS-25D engines will be flown at 109%. The new RS-25E engines will be flown at 111%. From page 25 of the attached document. The RS-25D has been certified at 109% and also ground tested at 111%.

My understanding is that the existing RS-25D engines will be flown at 109%. The new RS-25E engines will be flown at 111%. From page 25 of the attached document. The RS-25D has been certified at 109% and also ground tested at 111%.

Although RS-25D has been tested at 111%, that does not mean that it is certified for 111% which I believe requires additional testing or modifications to the engine.

That is my understanding of the situation. Attempts to certify 109% and 111% for nominal flight were squashed, with the 109% option for extreme contingencies.

Source Wayne Hale:"During testing to certify the 109% for aborts, it was found that there were components in the main propulsion piping in the orbiter which likely could not withstand the higher vibration environment associated with that flow rate. Cracking of the metallic components could have lead to liberation of metal pieces into the engine inlet which would not have been good at the pumps. So efforts to certify 109% or 111% were terminated. 109% throttles were authorized only in 'do or die' contingency abort scenarious which were multiple failures deep."

I understood that the RS-25E would be a simplified design using modern manufacturing techniques, and a considerably reduced part count. So where does the extra ~300 lbs for the new engine come from?

Is the new channel-wall nozzle that much heavier than the legacy tube-wall version?

The legacy tube wall nozzle is 130lbs lighter than the "new" channel-wall nozzle, at least when compared in the Block III SSME proposal. The Block III SSME was projected to be approx. 400lbs heavier than Block II SSME.Of course there is the question of just how similar will the RS-25E be to the Block III proposals?

The Block III proposal offers greater thrust for contingency aborts than Block II did, sounds like 111% was on the table for contingency aborts for the Block III SSME.

The environment in which these controllers reside must be rather challenging, what with the acoustics/vibration as well as thermal. Is the idea to replace the software and some of the hardware, but keep the outer casing and interfaces the same?

As I recall, there weren't all that many of the Block II SSME controllers ever built -- on the order of 10 or so. That's a good plan when you're recovering and re-using the engines, but not so good when you're tossing them in the ocean four at a time. Since you'd need to build new hardware anyway (even if you used "stock" SSMEs & controllers for the first flights), it makes sense to build newer (hopefully, cheaper) controllers and use them from the start. Obviously, the new controller needs to interface with the standard with both the stock SSME as well as the new-built RS-25E for this to make sense.

IIRC the new RS-25 controller and the new J2X controller are one in the same. So Block II SLS will use a common controller on bothe the core and the upper stage.

Unlikely. SLS, as currently envisioned up to the 130 mT version, will never fly J-2X on any upper stage.

Including or not including the Block II 130mt SLS? I understand that anything on the books is not Block II related.

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Edit: It appears that the RS-25 "Controller development is based heavily on the recent development experience with the J-2X engine controller".

But then there is this quote "You can't put yesterday's hardware on today's engine, especially since many parts of the shuttle-era engine controller unit aren't even made anymore," said Russ Abrams, avionics subsystem manager in the SLS Liquid Engines Office at NASA's Marshall Space Flight Center in Huntsville, Alabama"